Bar-J Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bar-J Ranch clear sky chart from 2005-11-05 to 2017-12-02.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
43%
16207
28%
47812
14%
16161
57%
16161
42%
24866

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
30%
885
31%
2491
11%
880
50%
880
48%
1212
January16th to endNight
27%
768
35%
2496
15%
768
50%
768
48%
1091
February1st to 15thNight
23%
702
26%
2246
7%
698
44%
698
40%
1108
February16th to endNight
23%
632
37%
1894
7%
632
53%
632
44%
932
March1st to 15thNight
33%
720
29%
2088
11%
720
50%
720
45%
1030
March16th to endNight
34%
694
31%
2038
12%
694
52%
694
40%
1057
April1st to 15thNight
34%
539
26%
1798
12%
539
53%
539
35%
888
April16th to endNight
33%
540
24%
1800
12%
540
52%
540
30%
990
May1st to 15thNight
41%
539
21%
1662
13%
539
51%
539
28%
1000
May16th to endNight
47%
562
19%
1498
9%
561
56%
561
37%
884
June1st to 15thNight
57%
540
24%
1440
14%
540
65%
540
50%
745
June16th to endNight
67%
540
25%
1440
19%
540
71%
540
50%
762
July1st to 15thNight
67%
510
16%
1360
14%
510
68%
510
31%
881
July16th to endNight
73%
564
14%
1503
14%
531
74%
531
31%
941
August1st to 15thNight
69%
539
14%
1674
13%
536
70%
536
29%
1016
August16th to endNight
70%
573
23%
1910
25%
573
72%
573
33%
1077
September1st to 15thNight
66%
540
24%
1800
22%
540
72%
540
33%
1021
September16th to endNight
61%
543
34%
1926
27%
543
73%
543
44%
892
October1st to 15thNight
50%
720
31%
2160
18%
720
61%
720
47%
1103
October16th to endNight
50%
768
39%
2304
19%
768
65%
768
50%
1112
November1st to 15thNight
42%
944
35%
2464
15%
944
54%
944
57%
1200
November16th to endNight
37%
975
40%
2584
14%
975
56%
975
57%
1242
December1st to 15thNight
26%
910
27%
2548
6%
910
44%
910
44%
1285
December16th to endNight
26%
960
29%
2688
7%
960
45%
960
42%
1397

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
442442445%8%54%
48639
Night
341332345%7%60%
47992
TransparencyDay
25%5%13%25%22%7%
48322
Night
22%5%14%28%22%6%
47812
SeeingDay
11%15%32%25%13%2
6013
Night
6%9%35%34%13%
16211

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
412323346%66%
1456
16th to endDay
1313312247%66%
1728
February1st to 15thDay
15%25%21335%8%59%
1615
16th to endDay
42432245%7%62%
1580
March1st to 15thDay
2424423348%57%
1869
16th to endDay
26%244345%5%8%51%
2185
April1st to 15thDay
36%344345%48%52%
2150
16th to endDay
8%9%35%4345%5%5%45%
2160
May1st to 15thDay
7%6%35%5%25%6%6%7%41%
2283
16th to endDay
6%5%24435%5%6%8%47%
2616
June1st to 15thDay
4413426%5%7%9%50%
2520
16th to endDay
3213425%5%6%8%55%
2520
July1st to 15thDay
7%425%5%46%5%6%9%43%
2520
16th to endDay
5%5%25%5%5%7%6%7%9%37%
2559
August1st to 15thDay
7%5%35%6%46%5%6%8%39%
2277
16th to endDay
6%5%244345%7%8%45%
2292
September1st to 15thDay
6%5%244245%7%7%48%
2160
16th to endDay
6%313323345%62%
2030
October1st to 15thDay
4313314346%62%
1800
16th to endDay
3412213345%66%
1913
November1st to 15thDay
213212247%71%
1718
16th to endDay
213212228%71%
1703
December1st to 15thDay
424212348%63%
1449
16th to endDay
221321245%9%61%
1536
January1st to 15thNight
312222347%68%
2491
16th to endNight
1213212335%71%
2496
February1st to 15thNight
1424312337%63%
2236
16th to endNight
424322346%65%
1894
March1st to 15thNight
141331236%8%62%
2088
16th to endNight
25%24214246%62%
2038
April1st to 15thNight
36%23213347%61%
1798
16th to endNight
9%8%23323346%53%
1800
May1st to 15thNight
9%8%3433345%6%46%
1661
16th to endNight
8%4232245%6%7%52%
1497
June1st to 15thNight
421221335%10%62%
1440
16th to endNight
421221346%8%62%
1440
July1st to 15thNight
8%4246%35%7%7%9%41%
1440
16th to endNight
5%3245%36%7%9%12%39%
1606
August1st to 15thNight
5%3246%35%5%8%8%46%
1683
16th to endNight
6%424335%5%6%9%46%
1910
September1st to 15thNight
8%5%1443447%9%46%
1800
16th to endNight
6%312213346%62%
1926
October1st to 15thNight
4412213445%65%
2160
16th to endNight
341221335%6%65%
2304
November1st to 15thNight
1112312347%70%
2464
16th to endNight
1311212347%70%
2584
December1st to 15thNight
324322246%66%
2548
16th to endNight
132432245%7%62%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
17%314%38%23%2
1457
16th to endDay
18%213%35%24%5%
1728
February1st to 15thDay
20%5%14%36%18%4
1616
16th to endDay
20%310%30%28%6%
1580
March1st to 15thDay
22%311%27%28%6%
1869
16th to endDay
27%6%10%27%23%4
2185
April1st to 15thDay
27%411%28%20%7%
2150
16th to endDay
37%5%9%22%20%5%
2160
May1st to 15thDay
35%8%14%20%17%2
2283
16th to endDay
30%7%15%20%18%7%
2620
June1st to 15thDay
25%6%14%18%21%13%
2520
16th to endDay
22%6%10%19%27%13%
2520
July1st to 15thDay
34%7%14%18%16%7%
2371
16th to endDay
35%9%18%20%11%3
2400
August1st to 15thDay
35%10%14%17%15%6%
2262
16th to endDay
30%6%14%23%19%4
2292
September1st to 15thDay
29%5%14%22%19%8%
2160
16th to endDay
21%39%24%31%8%
2030
October1st to 15thDay
20%410%23%30%10%
1800
16th to endDay
19%27%28%31%9%
1913
November1st to 15thDay
14%210%26%33%11%
1718
16th to endDay
14%26%35%30%10%
1703
December1st to 15thDay
18%417%34%20%3
1449
16th to endDay
19%5%20%32%17%5%
1536
January1st to 15thNight
16%317%33%25%3
2491
16th to endNight
15%314%33%26%5%
2496
February1st to 15thNight
21%416%36%17%3
2246
16th to endNight
19%210%32%28%6%
1894
March1st to 15thNight
18%413%30%29%4
2088
16th to endNight
21%5%11%31%26%2
2038
April1st to 15thNight
22%5%12%29%22%6%
1798
16th to endNight
31%413%26%18%5%
1800
May1st to 15thNight
35%6%14%22%17%4
1662
16th to endNight
26%8%18%21%17%8%
1498
June1st to 15thNight
17%6%18%22%17%17%
1440
16th to endNight
19%6%13%23%20%16%
1440
July1st to 15thNight
34%10%15%20%12%7%
1360
16th to endNight
31%11%25%20%8%2
1503
August1st to 15thNight
30%12%20%18%12%5%
1674
16th to endNight
29%8%17%27%13%3
1910
September1st to 15thNight
29%8%16%21%15%8%
1800
16th to endNight
21%311%28%28%7%
1926
October1st to 15thNight
20%5%11%22%29%10%
2160
16th to endNight
18%38%27%32%8%
2304
November1st to 15thNight
13%212%29%30%10%
2464
16th to endNight
13%29%33%32%7%
2584
December1st to 15thNight
19%317%34%22%2
2548
16th to endNight
19%5%19%30%20%3
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
8%14%37%24%14%
90
16th to endDay
7%7%40%38%6%
96
February1st to 15thDay
11%21%44%20%3
90
16th to endDay
8%20%39%18%11%1
81
March1st to 15thDay
15%18%40%20%5%
159
16th to endDay
18%33%36%10%1
288
April1st to 15thDay
14%37%29%13%4
269
16th to endDay
24%35%29%9%1
270
May1st to 15thDay
12%20%37%22%6%1
375
16th to endDay
12%14%34%24%12%
517
June1st to 15thDay
7%13%31%29%14%3
495
16th to endDay
410%31%29%21%3
495
July1st to 15thDay
10%5%24%26%26%5%
475
16th to endDay
9%321%34%27%4
418
August1st to 15thDay
13%6%33%29%13%3
315
16th to endDay
13%5%31%30%15%2
332
September1st to 15thDay
8%14%37%23%13%2
315
16th to endDay
11%12%34%26%11%3
194
October1st to 15thDay
8%14%22%35%14%2
135
16th to endDay
7%14%29%24%20%2
144
November1st to 15thDay
5%12%28%31%17%3
135
16th to endDay
11%13%42%28%2
135
December1st to 15thDay
8%19%55%15%1
94
16th to endDay
5%20%45%23%31
96
January1st to 15thNight
315%47%25%7%1
885
16th to endNight
213%50%25%6%
768
February1st to 15thNight
5%11%54%26%2
704
16th to endNight
216%53%23%3
632
March1st to 15thNight
415%42%32%6%
720
16th to endNight
6%12%43%32%5%
694
April1st to 15thNight
6%17%36%33%5%
539
16th to endNight
13%12%36%30%7%
540
May1st to 15thNight
13%8%29%37%9%
540
16th to endNight
11%7%28%36%15%
563
June1st to 15thNight
6%426%42%17%2
540
16th to endNight
4219%47%26%
540
July1st to 15thNight
9%19%39%37%3
510
16th to endNight
7%7%35%46%2
564
August1st to 15thNight
7%110%39%38%2
539
16th to endNight
7%19%40%37%3
573
September1st to 15thNight
9%214%43%27%3
540
16th to endNight
8%419%44%21%1
543
October1st to 15thNight
5%5%34%39%13%1
720
16th to endNight
5%5%33%38%15%
768
November1st to 15thNight
212%38%35%10%
944
16th to endNight
412%43%34%5%
975
December1st to 15thNight
214%52%25%3
910
16th to endNight
315%50%26%4
960
Page generated at 2017-12-03 09:16:48. Version ac04

Copyright 2017 A. Danko


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